A high-speed rail corridor is planned along the Rhine, from Frankfurt to Basel. It includes the NBS Frankfurt – Mannheim, and the ABS / NBS Karlsruhe – Basel, Some sections are already in use. There is no corresponding high-speed rail line (HSL) on the left bank, and no official plans for one. The incomplete HSL Paris – Strasbourg is at right angles to the river, and the planned Rhone – Rhine HSL does not extend to the Rhine valley.
There are geographic and historic reasons for the discrepancy: the largest urban centres are on the right (east) bank of the Rhine, and the region is historically disputed (Alsace-Lorraine question). Nevertheless, the Rhine corridor has enough strategic importance, to justify a parallel HSL on the left (west) bank. There are few topographic obstacles: the line would run through the Upper Rhine Plain, a rift valley.
The corridor is about 320 km long, from Basel to Mainz. It would start with a HSL Basel – Strasbourg- Karlsruhe, consisting of:
- an upgraded and 4-tracked line out of Basel;
- a new line by-passing Mulhouse, alongside the Autoroute A35, and rejoining the main line near Rouffach;
- an upgraded and 4-tracked line through Colmar and Strasbourg, crossing the Rhine over a new link to Karlsruhe.
Basel has 170 000 inhabitants, the metropolitan region about 800 000. It has two main stations, one on each bank of the Rhine. The Basel SBB Station, on the left bank, is the terminal for Swiss domestic services. However, the curving exit line toward St. Louis and Mulhouse can not be widened or improved, because it runs through dense urban areas. A new exit tunnel would mean demolition of an office building, and the loss of part of Basel Zoo.
Click to enlarge: schematic exit tunnel alignment…
It might be easier to start from the Badischer Bahnhof on the right bank, with a long tunnel to St. Louis. From there, in any case, the existing line toward Mulhouse would be 4-tracked.
The line is the 142-km Basel – Colmar – Strasbourg railway. The original alignment is good, and the gradient is very low (1 per 1000). Some demolition would be inevitable in the suburbanised villages between Basel and Mulhouse.
A new bypass of Mulhouse would save 10 km, and avoid the curves near Mulhouse station. The Autoroute A35 offers a suitable alignment, clear of the urban area. North of Rouffach, the new HSL would leave the A35, to rejoin the railway (4 km to the west). From there, there would again be 4 tracks, possibly with the HSL alongside the existing line. Although the alignment is good, it was not built for high-speed trains, and local improvement of the curves would be necessary.
All trains would stop at Colmar (population 120 000), so the curves at the station are not a problem. A restored Colmar – Freiburg line would connect the high-speed corridors on both sides of the Rhine. From Colmar to Strasbourg, the line runs mainly through open countryside: the last section is dead straight.
Just north of Strasbourg station, the line along the Rhine diverges from the line to Paris. This is the 56-km Strasbourg – Lauterbourg railway.
The Lauterbourg line is not as straight as that south of Strasbourg: if the alignment was a problem, the HSL could also follow the parallel Autoroute A35. About 35-45 km from Strasbourg, there would be a new high-speed link across the Rhine, connecting to the right-bank main lines, south of Karlsruhe. The new line could run near the old link across the river, from Roeschwoog to to Rastatt (Rheinbahn, circa 17 km). It could be further north, for instance Seltz – Durmersheim, with 4-tracks from Durmersheim to Karlsruhe. The Strasbourg – Karlsruhe section would be about 73 km long.
Click to enlarge: The lines south of Karlsruhe as built, from an Austro-Hungarian military map of around 1910, with a possible new link superimposed.
This is a minimal version of a Rhine left-bank HSL, providing a second high-speed route south of Karlsruhe. The line would be about 205 km long, from Basel to Karlsruhe. It would be logical to extend this HSL further north of Strasbourg: see the separate post Rhine left bank high-speed line, Strasbourg – Mainz.